Field of the Invention
The present invention relates to a plugged honeycomb structure and a plugged honeycomb segment. More particularly the present invention relates to a plugged honeycomb structure and a plugged honeycomb segment with low pressure loss and excellent thermal shock resistance.
Description of the Related Art
In recent years, there has been a demand for the reduction in fuel consumption of an automobile from the viewpoints of influences on the global environment and resource saving. This leads to a tendency of using internal combustion engines with good thermal efficiency, such as a direct injection type gasoline engine and a diesel engine, as a power source for an automobile.
Meanwhile, these internal combustion engines have a problem that soot is generated during combustion of the fuel. A countermeasure has been then required from the viewpoint of air environment to remove toxic components included in exhaust gas and to avoid the emission of particulate matter (hereinafter this may be called “PM”), such as soot or ash, to the air.
Especially there is a global tendency of tightening the regulations on removal of PM emitted from a diesel engine. Then a honeycomb-structured wall flow type exhaust gas purification filter has attracted the attention as a trapping filter (this may be called a “DPF”) to remove PM, and various systems for the filter have been proposed. Such a DPF is typically configured so that a plurality of cells serving as a through channel of fluid is defined by a porous partition wall, and by plugging the cells alternately, the porous partition wall defining the cells functions as a filter. A pillar-shaped structure including a plurality of cells defined by a porous partition wall may be called a “honeycomb structure”. Then a honeycomb structure including cells whose open ends are plugged with plugging portions may be called a “plugged honeycomb structure”. A plugged honeycomb structure is widely used as a trapping filter, such as a DPF. As exhaust gas containing particulate matter flows into the plugged honeycomb structure from the inflow end face (first end face), the particulate matter in the exhaust gas is filtered during the passing through the partition wall, and the purified gas is emitted from the outflow end face (second end face) of the plugged honeycomb structure.
Conventionally a plugged honeycomb structure includes the cells, such as quadrangular cells, hexagonal cells, and HAC cells (cells having the geometry that is the combination of octagons and quadrangles). Recently new plugged honeycomb structures have been developed, including the combination of cells of different shapes or having a feature in the position of plugging (see Patent Documents 1 and 2). Such plugged honeycomb structures can suppress cracks during burning of PM and can accumulate a lot of ash at the partition wall while reducing both of the pressure loss during the initial stage of the operation and the pressure loss after PM is accumulated.
[Patent Document 1] JP-A-2014-200741
[Patent Document 2] JP-A-2015-029939